Pigment

ABSTRACT

A pigment comprises a substrate, a metallic layer formed on at least one surface of the substrate and imparting metallic luster, and a transparent inorganic compound layer formed on surfaces of the substrate and the metallic layer. Thereby, the pigment produces color by light interference of a ray reflected on a surface of the transparent inorganic compound layer and a ray passed through the transparent inorganic compound layer and reflected on a surface of the metallic layer. Thus, the pigment is excellent in coloring power and hiding power, and particularly useful for an automotive finishing paint.

This is a division of application Ser. No. 07/306,980, filed Feb. 7,1989.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pigment producing interference color.The pigment of the present invention is particularly useful for anautomotive finishing paint.

2. Discussion of the Prior Art

A metallic paint containing aluminum flakes or other metal particles isvery popular as a finishing paint for automobiles, domestic electricappliances, etc. The aluminum flakes, however, are low in lightness andhard to produce light colors. Therefore, pearl mica has beenincreasingly used in recent years.

The pearl mica has a structure in which a surface of mica 100 is coveredwith a titanium dioxide layer 101, as shown in FIG. 8. An incident rayon this pearl mica is divided into a ray A which is reflected on asurface of the titanium dioxide layer 101 and a ray which passes throughthe titanium dioxide layer 101. The ray passed through the titaniumdioxide layer 101 is further divided into a ray B which is reflected ona surface of mica 100, and a ray which passes through mica 100.Reflected rays A and B produce various colors by light interference. Forexample, when the titanium dioxide layer 101 is 120-135 nm in thickness,pearl mica gives blue by light interference of rays A and B.

A part of the ray passing through the pearl mica reaches a surface of abase coat 102 and is then reflected on the base coat 102. The rayreturns back through the pearl mica and exits as a reflected ray C outof the titanium dioxide layer 101 on the incident side. Because thereflected ray C and reflected ray B are mixed and produce white color,interference of the reflected rays A and B is lessened and theinterference color is weakened.

Further, the pearl mica is poor in coloring power and hiding power. Forexample, an automotive metallic coating has been conventionally appliedby using a metallic paint and a clear paint in adouble-coating-single-curing operation. Thickness of the metallic paintfilm containing pearl mica at the time of complete hiding is generally200 μm or more. When the metallic paint containing the pearl mica isapplied by the conventional coating operation, color of a base coat isseen through the metallic paint film. Thus, uneven coating occurs hereand there and is hard to be corrected.

Therefore, as disclosed in Japanese Unexamined Patent Publication(KOKAI) No. 215857/1984, it has been conducted to apply a coloredintercoat which has the same or somewhat similar color to a givenmetallic paint containing pearl mica, and then apply the metallic paintcontaining pearl mica thereon. This method, however, requires as manyintercoats as metallic paints and additional coating processes, and hasresulted in increased production costs.

In order to overcome the disadvantages of the pearl mica, a coloringmica has been considered. In the coloring mica, as shown in FIG. 9, atitanium dioxide layer 201 formed on pearl mica 200 is covered with aniron oxide layer 202 such as a Fe₂ O₃ layer. This coloring mica givesinterference color and inherent color of iron oxide. Accordingly, colorpower and hiding power of the paint film containing the coloring mica ismuch enhanced compared with that containing the pearl mica.

The coloring mica pigment offers various colors by changing thickness ofthe titanium dioxide layer 201 or changing crystal structure of the ironoxide layer 202. However, because the color of this pigment is based onthe inherent color of iron oxide, color variety of the pigment isrestricted in the range from red to yellow. Further, because theinherent color of iron oxide is turbid, the coloring mica pigment offersless clear color than the inteference color. Research and developmenthave been conducted to add metals such as cobalt, copper, chromium,cadmium to mica pigments for the purpose of increasing the colorvariety, but have not reduced the paints into practical use because oftoxicity and poor durability.

On the other hand, as shown in FIG. 10, Japanese Unexamined PatentPublication (KOKAI) No. 60163/1985 discloses a pigment in which surfaceof mica 300 is coated with a titanium monoxide layer 301, and then atitanium dioxide layer 302 is formed thereon. Japanese Unexamined PatentPublication (KOKAI) No. 225264/1986 discloses a paint using thispigment. This pigment (hereinafter referred to as black pearl pigment)offers a less reflected ray C because the titanium monoxide layer 301 isdark brown and absorbs many rays passing through. Therefore,interference between reflected rays A and B is hardly disturbed by theray C and produces strong interference color. The black pearl pigmentproduces clear color with strong coloring power and hiding powercompared with the conventional pearl mica pigment.

The coloring power and hiding power of the black pearl pigment, however,are not strong enough to be used for an automotive finishing paint.Namely, even if the black pearl pigment is contained in the paint by themaximum amount without adversely affecting the paint film properties,the paint film thickness required for complete hiding is as high as80-100 μm and it is not practical enough.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide apigment, long required in the field of automotive finishing paint, whichproduces strong interference color and which is excellent in coloringpower and hiding power.

The pigment of the present invention comprises:

a substrate;

a metallic layer formed on at least one surface of the substrate andimparting metallic luster; and

a transparent inorganic compound layer formed on surfaces of thesubstrate and the metallic layer,

whereby the pigment produces color by light interference of a rayreflected on a surface of the transparent inorganic compound layer and aray passed through the transparent inorganic compound layer andreflected on a surface of the metallic layer.

The substrate according to the present invention has a powder or scalyshape. The scaly shape is particularly preferred for the substrate,because the scaly-shape substrate orients in multi-layers in a wet paintfilm, and the resulting paint film can have excellent hiding power andflip-flop characteristic. The flip-flop characteristic means the shiftin reflection color depending on angle of incidence and angle ofobservation. The substrate comprises any suitable materialconventionally used in this art including natural mica, synthetic mica,glass flakes and molybdenum disulfide. Natural mica and synthetic micaare particularly preferred as the substrate. The substrate is preferablyabout 0.5-2 μm in thickness and 50 μm or less in mean particle diameter.

The metallic layer is formed on at least one surface of the substrateand imparting matallic luster. The metallic layer can be formed on onlya part of the surface of the substrate, but preferably formed on theentire surface of the substrate. The metallic layer almost completelyreflects light which passed through the transparent inorganic compoundlayer, thereby producing strong interference color. The metallic layercomprises a metal such as silver, gold, copper, palladium, nickel andcobalt, or an alloy such as an Ni-P alloy, an Ni-B alloy, an Ni-Co-Palloy, an Ni-W-P alloy, an Ag-Au alloy and a Co-P alloy. The substratecan be formed entirely by such a metal.

The transparent inorganic compound layer is formed on surfaces of thesubstrate and the metallic layer. The inorganic compound layer maypreferably comprise titanium dioxide, iron oxide, aluminum hydroxide,chromium hydroxide or the like having a high index of refraction. Forthis reason, titanium dioxide is most preferred as the transparentinorganic compound layer. Various interference colors can be obtained bychanging material and thickness of the transparent inorganic compoundlayer.

Metal dots or alloy dots may be formed on the transparent inorganiccompound layer in a scattered manner. Metal dots or alloy dotscontribute to produce strong interference color since intensity of lightreflected on the surface of the inorganic compound layer is increased.

A method for producing the pigment according to the present inventioncomprises a first step of forming a metallic layer on a substrate suchas mica, and a second step of forming an inorganic compound layer onsurfaces of the substrate and the metallic layer. The first step may becarried out by a plating method such as electroplating and electrolessplating, or a physical vapor deposition method such as vacuumevaporation and sputtering. The second step may be carried out byconventional methods. For example, an aqueous solution of inorganic saltis adhered on the surfaces of the substrate, then the water-containinglayer is deposited by hydrosis, and finally the water-containing layeris heated at a certain temperature. When titanium dioxide is employedfor the inorganic compound layer, it can be formed by a titanyl sulfatemethod disclosed for example in Japanese Patent Examined Publication(KOUKOKU) No. 25644/1968 or a titanium tetrachloride method and thelike.

The present invention includes a pearl mica pigment in which a metalliclayer is formed between the mica and the titanium dioxide layer. So, itmay be taken into account to use pearl mica as a starting material forthe pigment of the present invention. But it has been very difficult toform a metallic layer on the surface of mica through the outermosttitanium dioxide layer. However, the inventors of the present inventionhave found after earnest studies that a metallic layer can be formed ona surface of mica through the titanium dioxide layer under specialconditions, and established a method of forming the metallic layerutilizing this phenomenon. The method will be explained hereinafter.

First, a titanium dioxide layer of a predetermined thickness is formedon a surface of mica by the titanyl sulfate method or other knownmethods. This step may be omitted by using commercially available pearlmica.

Then, the pearl mica is treated by chrome plating, namely, depositing achromium compound on the surface of the titanium dioxide layer. Forexample, as shown in U.S. Pat. No. 4,134,776, chromium hydroxide may bedeposited by hydrolyzing a solution of water-soluble chromium salts suchas chromium chloride and chromium sulfate. Or, as shown in German patentapplication No. P 32 03 017.1, chromium may be deposited as hydroxide,carbonate, phosphate or meta-acrylate complex by precipitating from asolution containing iron, manganese and chromium ions.

Next, the chrome plated pearl mica is subjected to electroless plating.The experiments conducted by the present inventors have shown, asdescribed in detail later in the preferred embodiment, that a metalliclayer is deposited not on the surface of the titanium dioxide layer buton an interface between the mica and titanium dioxide layer. The reasonshave not been entirely understood, but it has been discovered that thechromium compound remarkably decreases rate of electroless plating, andthe decreasing effect is assumed to greatly contribute to thisphenomenon. Thus, the metallic layer can be formed on a surface of thesubstrate comprising mica. In alumina-treated mica or untreated mica,however, the metallic layer is not deposited on the interface.

The decreasing effect is varied by the amount of the deposited chromiumcompound. For example, when silver is plated as a metallic layer byelectroless plating, the amount of the metal chromium contained in thedeposited chromium compound should be from 0.05 to 5 wt % based on 100wt % of pearl mica. When the amount of the metal chromium is less than0.05 wt %, silver is deposited on the surface of the titanium dioxidelayer and cannot produce desired interference color. When the amount ofthe deposited chromium compound is more than 5 wt %, the color ofchromium affects the color of the paint film and makes it yellowish.Particularly, the amount of the metal chromium is most preferred to befrom 0.15 to 0.30 wt %.

When silver is deposited on the interface for the metallic layer, silvermay be deposited in a range of from 1 to 100 wt % based on 100 wt % ofpearl mica. When silver is less than 1 wt %, the interference color isweak and the coloring power is poor. When silver is more than 100 wt %,silver particles having a mean diameter of several microns are depositedon the surface of the titanium dioxide layer, and desired color cannotbe obtained. The range of 0.1-10 wt % is particularly preferred. In thisrange, the deposited silver particles have a mean diameter of 10-500 nm,and can produce the strongest inferference color.

Hereinafter functions of the pigment according to the present inventionwill be explained with reference to FIG. 1.

The pigment according to the present invention comprises a substrate 1,a metallic layer 10 formed on at least one surface of the substrate 1,and a transparent inorganic compound layer 2 formed on surfaces of thesubstrate and the metallic layer. In this instance, the metallic layer10 is formed on an entire surface of the substrate 1.

When a ray enters into the pigment, a part of the incident ray isreflected on a surface of the inorganic compound layer 2 as a reflectedray A1. The rest of the incident ray passes through the inorganiccompound layer 2, is reflected on a surface of the metallic layer 10,and again passes through the inorganic compound layer 2 as a reflectedray A2. The reflected rays A1 and A2 produce interference color inaccordance with an optical thickness (geometrical thickness multipliedby refractive index) of the inorganic compound layer 2. Because themetallic layer 10 of the present invention has metallic luster, almostall the ray which has passed through the inorganic compound layer 2 andreached the metallic layer 10 is reflected on the metallic layer withoutloss. Thus, the reflected ray A2 has the maximum intensity and achievesthe maximum interference with the reflected ray A1, thereby producingthe strong infererence color. When the metallic layer 10 is formed onall the surfaces of the substrate 1, no ray passes through the pigmentand almost all the incident ray contributes to the interference. Thus,the strongest inferference color is obtained. The interference color canbe varied by changing the thickness of the inorganic compound layer 2.Further, the metallic luster of the metallic layer 10 can be seenthrough the outermost surface of the pigment. Consequently, the pigmentcan be used as a metallic pigment having various colors.

General coloring pigments produces colors by absorption of lights.Mixture of three primary colors becomes almost black. As the primarycolors are mixed more, the color saturation becomes lower. On the otherhand, though the inherent color of the pigment of the present inventionis achromatic color of metallic luster, the color of the pigment to beseen is produced by the light interference. Because the interferencecolor is produced optically, the mixture of three primary colors becomesalmost white. Namely, in the pigment of the present invention, themixture of the three primary colors becomes almost the metallic color ofthe metallic layer and the color saturation does not decrease.Therefore, even if a plurality of colors are mixed in the pigment of thepresent invention, the color saturation is high and the color hue isclear.

As described above, strong coloring power and excellent hiding power areobtained in the pigment of the present invention, because the pigment ofthe present invention produces strong interference color which cannot beobtained by the conventional mica pigment. Also the pigment of thepresent invention can produce various colors by changing thickness ofthe inorganic compound layer, and can produce metallic paint films withvivid colors which have not been available before. Thus, the pigment ofthe present invention is significantly useful for an automotivefinishing paint.

In the conventional metallic paint, various colors have been obtained bymixing organic pigments and aluminum flakes, however, color separationsometimes occurs due to difference in compositions and electricalproperties of the pigment. Also, a method for producing the metallicpaint by employing coloring pigments requires a step for dispersing thepigments by a ball mill or the like, and results in increased man-hourrequirement. On the other hand, the pigment of the present inventionnever generates color separation, because the chemical composition ofthe pigment is the same even when a plurality of the primary colors aremixed. Also, the pigment of the present invention requires no dispersingstep, and results in reduced man-hour requirement.

BRIEF DESCRIPTION OF THE DRAWINGS

The exact nature of this invention, as well as other objects andadvantages thereof, will be readily apparent from consideration of thefollowing description of preferred embodiments relating to theaccompanying drawings, in which:

FIG. 1 is a schematic cross-sectional view of a pigment of a preferredembodiment of the present invention;

FIGS. 2-5 show shematic illustrations of microscopic photographs ofsample pigment No. 5-C-3 of the preferred embodiment according to thepresent invention;

FIG. 6 is an enlarged cross-sectional view of a part of the pigment ofthe preferred embodiment of the present invention;

FIG. 7 is an enlarged plan view of the part of the pigment of thepreferred embodiment of the present invention;

FIG. 8 is a schematic cross-sectional view of a conventional pearl mica;

FIG. 9 is a schematic cross-sectional view of a conventional coloringmica; and

FIG. 10 is a schematic cross-sectional view of a conventional blackpearl pigment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A pigment of the preferred embodiment of the present invention comprisesa mica 1 as the substrate, a silver layer 10 formed on all the surfacesof mica 1 as the metallic layer, and a titanium dioxide layer 2 formedon all the surfaces of the silver layer 10 as the transparent inorganiccompound layer. The pigments of the preferred embodiment and thepigments of comparative examples will be explained in detail along withthe producing methods thereof. Parts and percentages used herein meanparts by weight and percentages by weight.

[Producing Pearl Mica]

Commercially available mica flakes of about 0.5-1.0 μm in thickness and10-50 μm in particle diameter were employed as the substrate, and atitanium dioxide layer was formed on the mica particles by a tytanylsulfate method. More specifically, 150 g of mica particles were added to750 ml of an aqueous solution of tytanyl sulfate containing 67% astitanium dioxide, and were rapidly heated and boiled for about 4.5 hourswhile refluxing. The resulting product was separated by filtering and bywashing with water to pH5.0.

Six different amounts of the mica particles were added for forming sixkinds of pearl mica having titanium dioxide layers with differentthickness. The respective pearl mica thus obtained were embedded inresins, sliced by a microtome and examined through a transmissionelectron microscope for measuring thickness of the titanium dioxidelayers.

Table 1 shows the thickness of the titanium dioxide layers along withhues of reflected and transmitted lights.

                  TABLE 1                                                         ______________________________________                                        Sample Thickness of Hue                                                       No.    TiO.sub.2 layer (nm)                                                                       Reflected light                                                                           Transmitted light                             ______________________________________                                        1-M    20-40                    silver                                        2-M    40-90        yellow      purple                                        3-M     90-110      red         blue                                          4-M    110-120      reddish purple                                                                            green                                         5-M    120-135      blue        orange                                        6-M    135-155      green       red                                           ______________________________________                                    

[Chrome-Plating]

Each pearl mica was dispersed in 100 g of distilled water to obtain asuspension. Then, 100 ml of an aqueous solution cotaining 92 g ofFeSO₄.7H₂ O, 17 g of KCr(SO₄)₂.12H₂ O and 100 ml of an aqueous solutioncontaining 1.5 g of NaH₂ PO₄.2H₂ O were added to the suspension at 50°C. for 60 minutes. The pH of the suspension was controlled at 4.5 byadding a 2% NaOH aqueous solution during the addition. After theaddition, the 2% NaOH aqueous solution was added to increase the pH to5.0 and the suspension was stirred for 60 minutes. Then, the suspensionwas filtered and the obtained material was washed and dried at 130° C.In this case, chromium phosphate as the chromium compound was depositedon the pearl mica. The amounts and time required for adding the twoaqueous solutions to the suspension for the chrome-plating were variedto produce four kinds of chrome-plated pearl mica with different amountsof deposited chromium compounds. The four kinds of chrome-plated pearlmica were respectively examined on the amount of deposited chromiumcompounds by plasma element analysis. The results of the analysis areshown in Table 2. The four kinds of the chrome-plating conditions i.e.,the four addition conditions were applied to each of the aforementionedsix pearl micas. Thus, a total of 24 kinds of chrome-plated pearl micaswere prepared. Also, pearl mica free from the chrome-plating and aluminaplated pearl mica were also prepared for comparison. Table 2 also liststhe sample numbers.

                                      TABLE 2                                     __________________________________________________________________________          Deposited                                                                             Sample No.                                                      Treatment                                                                           amount (wt %)                                                                         1-M  2-M  3-M  4-M  5-M  6-M                                    __________________________________________________________________________    chrome-                                                                             0.10    1-C-1                                                                              2-C-1                                                                              3-C-1                                                                              4-C-1                                                                              5-C-1                                                                              6-C-1                                  plating                                                                             0.20    1-C-2                                                                              2-C-2                                                                              3-C-2                                                                              4-C-2                                                                              5-C-2                                                                              6-C-2                                        0.30    1-C-3(*)                                                                           2-C-3(*)                                                                           3-C-3(*)                                                                           4-C-3(*)                                                                           5-C-3(*)                                                                           6-C-3(*)                                     0.50    1-C-4                                                                              2-C-4                                                                              3-C-4                                                                              4-C-4                                                                              5-C-4                                                                              6-C-4                                  none  --      1-A-1                                                                              2-A-1                                                                              3-A-1                                                                              4-A-1                                                                              5-A-1(*)                                    alumina-                                                                            0.50    1-A-2                                                                              2-A-2                                                                              3-A-2                                                                              4-A-2                                                                              5-A-2                                       plating                                                                       __________________________________________________________________________

[Formation of Metallic Layer]

15 g of each sample shown in Table 2 was dispersed and stirred in 450 mlof distilled water to obtain a suspension. 30 ml of silver solution,which was prepared by adding 50 g of AgNO₃ and 50 ml of an aqueoussolution of 28% ammonia to distilled water to make a total of 1 l of thesolution, was added to the suspension all at once at room temperature,and stirred for 5 minutes. Then 20 ml of formalin solution, which wasprepared by adding 9 ml of a solution of 35% formalin to distilled watermake a total of 40 ml of the solution, was added all at once, andstirred for 55 minutes. Thus, electroless plating was carried out. Thesuspension was filtered and the filtered material was washed and driedat 120° C. to obtain 36 kinds of pigments of the present invention andthe comparative examples. The same sample numbers as shown in Table 2were assigned to the pigments thus obtained.

Seven samples marked with asterisk (*) shown in Table 2 were subjectedto electroless plating by using 30 ml of two types of silver solutionswhich contained 100 g and 300 g of AgNO₃ in 1 l, respectively, to obtain14 pigments. Sample numbers of these pigments were shown in Table 3.Also, black pearl pigments of red, green, and black disclosed inJapanese Unexamined Patent Publication (KOKAI) No. 225264/1986 wereselected. Sample numbers of these black pearl pigments are B-1, B-2, andB-3, respectively.

                                      TABLE 3                                     __________________________________________________________________________    Sample No.                                                                           1-C-3 2-C-3 3-C-3 4-C-3 5-C-3 6-C-3 5-A-1                              __________________________________________________________________________    AgNO.sub.3 100 g                                                                     1-C-3-D-1                                                                           2-C-3-D-1                                                                           3-C-3-D-1                                                                           4-C-3-D-1                                                                           5-C-3-D-1                                                                           6-C-3-D-1                                                                           5-A-1-D-1                          AgNO.sub.3 300 g                                                                     1-C-3-D-2                                                                           2-C-3-D-2                                                                           3-C-3-D-2                                                                           4-C-3-D-2                                                                           5-C-3-D-1                                                                           5-C-3-D-2                                                                           5-A-1-D-2                          __________________________________________________________________________

[Pigment Structure Analysis]

The structure of the pigment of sample No. 5-C-3 was analyzed with thetransmission electron microscope. FIGS. 2-5 show the microscopicphotographs of the surface of the mica 1 and the side view of thetitanium dioxide layer 2. The titanium dioxide layer 2 and the mica 1have been separated.

The titanium dioxide layer 2 was observed, as schematically shown inFIGS. 6 and 7, that columnar titanium dioxide particles 20 of 10-100 nmin height and 2-5 nm in mean diameter were arranged orderly. The surfaceof mica 1 were observed that it comprises concentrically circularportions free from deposition and the silver particles 11 depositedaround the concentrically circular portions. This was supposed toindicate that the silver particles 11 were deposited around the titaniumdioxide particles 20. Thus, as shown in FIGS. 6 and 7, it is assumedthat the silver particles 11 were deposited between the titanium dioxidelayer 2 and the mica 1, and more specifically on the gaps between thetitanium dioxide particles 2.

[Production of Paint]

The aforementioned fifty-three samples and the six pearl micas shown inTable 1 which were neither chrome plated nor silver plated wereemployed, and the compositions shown below (all were solid except fororganic solvent) were mixed, and stirred to disperse with a high speeddisperser, thereby obtaining base metallic paints.

    ______________________________________                                        sample pigment        3.20%                                                   acrylic resin         18.78%                                                  melamine resin        8.05%                                                   suspending agent      1.96%                                                   additive              0.42%                                                   organic solvent       67.59%                                                  total                 100.00%                                                 ______________________________________                                    

The acrylic resin employed had the following monomer composition, andmade to a resin of weight average molecular weight (Mw) of 27000 andnumber of average molecular weight (Mn) of 12000.

    ______________________________________                                        stylene                20.0%                                                  n-butyl methacrylate   15.0%                                                  ethyl hexyl methacrylate                                                                             20.0%                                                  stearyl metacrylate    15.0%                                                  butyl acrylate         13.5%                                                  hydroxy metacrylate    15.0%                                                  methacrylic acid       1.5%                                                   total                  100.0%                                                 ______________________________________                                    

                  TABLE 4-1                                                       ______________________________________                                        Sample                                                                              CH               MCH                                                    No.   1*     a*       b*     1*    a*     b*                                  ______________________________________                                        1-C-1 39.61  -1.76    -1.06  58.26 -2.00   -3.10                              1-C-2 38.05  -1.20    -0.90  56.25 -1.50   -2.80                              1-C-3 34.08  -1.18    -3.86  54.51 -2.03   -6.54                              1-C-4 29.91  -1.04    -3.39  50.93 -1.35   -5.67                              2-C-1 32.10   0.60     7.30  46.09  1.70   16.20                              2-C-2 30.15   0.77     9.65  45.34  1.87   17.87                              2-C-3 29.20   1.34     10.97 45.21  2.12   18.90                              2-C-4 28.37   1.49     12.22 45.10  2.22   20.06                              3-C-1 25.43   4.99     5.30  32.90  9.60   -4.30                              3-C-2 23.42   5.74     6.44  32.23  9.71   -4.45                              3-C-3 20.31   6.18     5.14  30.41  11.30  -6.04                              3-C-4 18.58   6.64     3.40  29.71  11.56  -6.85                              4-C-1 25.20   3.70    -2.10  32.05  9.05  -12.10                              4-C-2 23.42   3.89    -2.29  31.48  9.41  -13.22                              4-C-3 20.24   4.98    -3.71  29.77  10.63 -14.70                              4-C-4 18.75   5.23    -4.65  28.99  11.27 -15.52                              5-C-1 25.90  -0.63    -6.90  36.80 -3.32  -18.08                              5-C-2 24.84  -0.62    -7.59  36.94 -3.34  -19.08                              5-C-3 22.39  -0.68    -8.96  35.56 -3.85  -20.38                              5-C-4 21.46  -1.54    -10.16 35.00 -4.13  -21.14                              6-C-1 29.05  -2.50     3.05  43.90 -9.00    9.30                              6-C-2 28.32  -2.73     3.68  43.46 -9.28    9.48                              6-C-3 25.75  -3.25     4.51  42.66 -9.92   10.58                              6-C-4 24.59  -3.84     4.59  42.26 -10.34  10.91                              ______________________________________                                    

                  TABLE 4-2                                                       ______________________________________                                        Sample   CH              MCH                                                  No.      1*     a*      b*     1*   a*     b*                                 ______________________________________                                        1-A-1    45.78  -2.90   -4.87  55.76                                                                              -3.13   -6.14                             1-A-2    41.05  -1.80   -4.50  53.20                                                                              -3.09   -5.80                             1-M      56.01  -0.20   -0.05  57.50                                                                              -0.20   -0.05                             2-A-1    52.02   2.44    21.53 58.06                                                                               1.26   22.65                             2-A-2    51.03   2.00    20.43 57.06                                                                               1.00   21.05                             2-M      59.23  -0.76   -3.58  68.16                                                                               0.73    6.75                             3-A-1    42.67   11.76   6.37  48.04                                                                               13.91   2.65                             3-A-2    41.30   10.98   5.99  43.05                                                                               12.22   2.55                             3-M      63.09   0.87    0.29  65.73                                                                               6.41   -0.91                             4-A-1    39.57   10.98  -9.05  46.79                                                                               12.85 -15.01                             4-A-2    38.79   11.90  -9.00  45.79                                                                               11.70 -14.99                             4-M      61.86  -0.45   -2.01  63.76                                                                               5.86  -11.76                             5-A-1    46.00  -3.83   -16.26 51.99                                                                              -4.71  -19.07                             5-A-2    45.88  -3.77   -15.99 51.00                                                                              -4.66  -18.85                             5-M      61.78  -1.02   -1.63  66.37                                                                              -3.82  -12.59                             6-A-1    46.34  -6.38    7.61  57.06                                                                              -10.88  12.89                             6-A-2    61.44  -2.21    0.98  67.80                                                                              -5.98    3.55                             6-M      63.55  -2.36    1.00  68.97                                                                              -6.03    3.76                             1-C-3-D-1                                                                              29.05  -1.02   -3.11  49.50                                                                              -1.21   -5.13                             1-C-3-D-2                                                                              25.31  -0.93   -2.78  44.12                                                                              -1.33   -4.98                             2-C-3-D-1                                                                              28.10   1.31    11.15 43.10                                                                               2.01   18.06                             2-C-3-D-2                                                                              26.10   1.45    10.95 41.91                                                                               2.04   17.99                             3-C-3-D-1                                                                              18.40   6.50    3.31  27.99                                                                               11.41  -6.71                             3-C-3-D-2                                                                              17.95   6.43    3.09  27.12                                                                               11.32  -5.96                             4-C-3-D-1                                                                              18.71   5.11   -4.52  27.12                                                                               11.12 -15.43                             4-C-3-D-2                                                                              17.91   5.07   -4.12  26.09                                                                               10.98 -15.36                             5-C-3-D-1                                                                              21.32  -1.48   -10.02 34.71                                                                              -3.92  -21.02                             5-C-3-D-2                                                                              20.13  -1.22   -9.41  33.99                                                                              -3.54  -20.95                             6-C-3-D-1                                                                              24.12  -3.50    4.12  41.12                                                                              -9.52   10.72                             6-C-3-D-2                                                                              22.09  -2.98    3.76  40.09                                                                              -8.21    9.98                             5-A-1-D-1                                                                              43.72  -2.99   -13.21 50.09                                                                              -4.21  -17.62                             5-A-1-D-2                                                                              41.11  -2.81   -11.95 49.01                                                                              -3.88  -17.00                             B-1      37.74   1.11   -4.72  47.86                                                                               10.83 -10.01                             B-2      41.58  -8.25   -0.11  50.77                                                                              -13.03   6.30                             B-3      35.18  -5.89   -11.68 43.89                                                                              -8.3   -22.69                             ______________________________________                                    

                  TABLE 5-1                                                       ______________________________________                                               Black & white                                                          Sample hiding film                                                                              40° C. water                                                                      80° C. water                                                                    ΔE after                          No.    thickness  resistance test                                                                          resistance test                                                                        QUV test                                ______________________________________                                        1-C-1  46         excellent  excellent                                                                              0.41                                    1-C-2  48         excellent  excellent                                                                              0.38                                    1-C-3  42         excellent  excellent                                                                              0.22                                    1-C-4  44         excellent  excellent                                                                              0.43                                    2-C-1  41         excellent  excellent                                                                              0.21                                    2-C-2  39         excellent  excellent                                                                              0.25                                    2-C-3  45         excellent  excellent                                                                              0.41                                    2-C-4  42         excellent  excellent                                                                              0.50                                    3-C-1  39         excellent  excellent                                                                              0.33                                    3-C-2  38         excellent  excellent                                                                              0.38                                    3-C-3  37         excellent  excellent                                                                              0.21                                    3-C-4  39         excellent  excellent                                                                              0.31                                    4-C-1  39         excellent  excellent                                                                              0.40                                    4-C-2  38         excellent  excellent                                                                              0.51                                    4-C-3  37         excellent  excellent                                                                              0.49                                    4-C-4  37         excellent  excellent                                                                              0.28                                    5-C-1  37         excellent  excellent                                                                              0.61                                    5-C-2  36         excellent  excellent                                                                              0.23                                    5-C-3  37         excellent  excellent                                                                              0.41                                    5-C-4  38         excellent  excellent                                                                              0.18                                    6-C-1  41         excellent  excellent                                                                              0.55                                    6-C-2  38         excellent  excellent                                                                              0.48                                    6-C-3  40         excellent  excellent                                                                              0.45                                    6-C-4  42         excellent  excellent                                                                              0.41                                    ______________________________________                                    

                  TABLE 5-2                                                       ______________________________________                                               Black & white                                                          Sample hiding film                                                                              40° C. water                                                                      80° C. water                                                                    ΔE after                          No.    thickness  resistance test                                                                          resistance test                                                                        QUV test                                ______________________________________                                        1-A-1  82         fair       poor     1.39                                    1-A-2  88         good       fair     1.11                                    1-M    390        excellent  excellent                                                                              0.51                                    2-A-1  79         fair       poor     1.55                                    2-A-2  78         good       fair     1.23                                    2-M    410        excellent  excellent                                                                              0.42                                    3-A-1  77         fair       poor     1.99                                    3-A-2  76         good       fair     1.34                                    3-M    380        excellent  excellent                                                                              0.38                                    4-A-1  75         fair       poor     2.23                                    4-A-2  74         good       fair     1.43                                    4-M    320        excellent  excellent                                                                              0.23                                    5-A-1  79         fair       poor     2.11                                    5-A-2  78         good       fair     1.33                                    5-M    400        excellent  excellent                                                                              0.49                                    6-A-1  72         fair       poor     2.33                                    6-A-2  77         good       fair     1.32                                    6-M    350        excellent  excellent                                                                              0.43                                    ______________________________________                                    

                  TABLE 5-3                                                       ______________________________________                                                Black & white                                                                            40° C.                                              Sample  hiding film                                                                              water re- 80° C. water                                                                    ΔE after                          No.     thickness  sistance test                                                                           resistance test                                                                        QUV test                                ______________________________________                                        1-C-3-D-1                                                                             41         excellent excellent                                                                              0.42                                    1-C-3-D-2                                                                             24         excellent excellent                                                                              0.38                                    2-C-3-D-1                                                                             38         excellent excellent                                                                              0.33                                    2-C-3-D-2                                                                             22         excellent excellent                                                                              0.41                                    3-C-3-D-1                                                                             37         excellent excellent                                                                              0.28                                    3-C-3-D-2                                                                             21         excellent excellent                                                                              0.31                                    4-C-3-D-1                                                                             36         excellent excellent                                                                              0.45                                    4-C-3-D-2                                                                             22         excellent excellent                                                                              0.46                                    5-C-3-D-1                                                                             35         excellent excellent                                                                              0.44                                    5-C-3-D-2                                                                             19         excellent excellent                                                                              0.39                                    6-C-3-D-1                                                                             39         excellent excellent                                                                              0.38                                    6-C-3-D-2                                                                             23         excellent excellent                                                                              0.32                                    5-A-1-D-1                                                                             65         fair      poor     1.73                                    5-A-1-D-2                                                                             63         good      fair     1.95                                    B-1     93         fair      poor     2.23                                    B-2     95         fair      poor     2.41                                    B-3     101        fair      poor     7.85                                    ______________________________________                                    

The melamine resin employed was n-butyl melamine resin ('u-van 20SE'produced by Mitsui Touatsu Chemical Co., Ltd.), and the suspending agentemployed was amide wax. Concentration of mica pigment was 10% by weight.

[Colorimetry]

The paints obtained from respective pigment samples were applied on thesurface of the gray-color intercoat film by a bar coater, baked anddried to be 15 μm in thickness when the film was dried. The color of thepaint film thus coated was measured by a colorimeter (`SM-3` produced bySuga Testing Machine Co., Ltd.), and the values L*, a*, b* (L*:lightness index, a*,b*: chromaticness indexes) are shown in Table 4.Colorimetry was conducted on both MCH which corresponds to the colorviewed at the front and CH which corresponds to the color viewed in anoblique direction.

[Hiding Power]

Respective paints were applied on a black and white paper for testinghiding power by changing film thickness. Table 5 shows the hiding filmthickness, i.e., the film thickness at which black and white cannot beidentified.

[Characteristics of Paint Film]

In order to prepare test pieces, each metallic paint was applied by airspray, on a steel plate which had been coated with an electrodepositedcoat and an intercoat film, so that the metallic paint film thicknesswas 15 μm when dried. After several minutes of flash-off time,acrylmelamine resin clear paint was applied by air spray on the metallicpaint film in a wet-on-wet manner so that the clear paint film thicknesswas 35 μm. Then, the test piece was baked at 140° C. for 23 minutes.Compositions of the clear paint and the acrylic resin used in the clearpaint are shown below.

    ______________________________________                                        <Clear Paint Composition>                                                     acrylic resin           38.25%                                                melamine resin          16.40%                                                additive                1.24%                                                 organic solvent         45.11%                                                total                   100.00%                                               <Acrylic Resin Composition>                                                   stylene                 30.0%                                                 n-butyl methacrylate    15.0%                                                 ethyl acrylate          20.0%                                                 butyl acrylate          17.5%                                                 hydroxy ethyl methacrylate                                                                            15.0%                                                 acrylic acid            2.5%                                                  total                   100.0%                                                ______________________________________                                    

Mw=16000 Mn=7000

The test pieces thus obtained were examined on water resistance andweather resistance. Water resistance tests were carried out under twodifferent conditions. One was conducted by immersing the test pieces inwarm water of 40° C. for 10 days. The other was conducted by immersingthe test pieces in hot water of 80° C. for 10 days. The appearances ofthe coated surfaces of the test pieces were visually inspected. Theweather resistance test was conducted by subjecting the test pieces to aCyclic Ultraviolet Weathering Tester (QUV) for 500 hours, and the colorsbefore and after the weather test was measured by the colorimeter. Theresults of the water resistance tests and the weather resistance testare also shown in Table 5.

[Evaluation]

When the pigment concentration by weight was 10%, the pigments of thepreferred embodiments according to the present invention (referred to as"C" series) had the black-and-white hiding film thickness of 21-48 μm,while the black pearl pigments (referred to as "B" series) had theblack-and-white hiding film thickness of 93-101 μm and the pearl micas(referred to as "M" series) had the black-and-white hiding filmthickness of 320-410 μm. It is apparent that the pigments of the presentinvention are excellent in coloring power and hiding power.

The pigments of C series had color degradation after the weatherresistance test as low as that of the pearl micas. It was not observedthat chrome-plating and silver-plating had deteriorated the weatherresistance. The pigments of the present invention maintain the excellentproperties. The pigments of C series were excellent in water resistanceand weather resistance compared with the pigments of A series free fromchrome-plating. It is apparent that chrome-plating improves water andweather resistances of the pigments.

Moreover, the pigments of C series showed big difference between MCH andCH, and offered excellent flip-flop characteristic. Also, as apparentfrom the black-and-white hiding film thickness of D series, theblack-and-white hiding film thickness decreased as the amount of thesilver plating increased. This is because the ratio of the ray totallyreflected on the surface of the silver plating layer to the incident rayon the pigment increases and the interference increases accordingly.

The pearl mica free from chrome-plating and the pearl mica with aluminatreatment, which were both subjected to the silver plating, of A seriesexhibited less flip-flop characteristic and greater black-and-whitehiding film thickness, compared with the chrome-plated pigments of Cseries. Although no illustration is provided herein, observation withthe microscope showed that silver particles were deposited on thesurface of the titanium dioxide layer.

Therefore, the pigments of C series according to the present inventionare satisfactorily applicable to an automotive finishing paint.

                                      TABLE 6-1                                   __________________________________________________________________________    RATIO OF                                                                              CH              MCH                                                   MIXTURE 100/0                                                                             75/25                                                                             50/50                                                                             25/75                                                                             100/0                                                                              75/25                                                                              50/50                                                                             25/75                                   __________________________________________________________________________    3-C-3/2-C-3                                                                         L*                                                                              28.26                                                                             29.04                                                                             30.60                                                                             30.92                                                                             40.77                                                                              43.19                                                                              45.71                                                                             47.69                                         a*                                                                              5.62                                                                              4.85                                                                              3.66                                                                              2.09                                                                              11.32                                                                              8.17 5.36                                                                              2.94                                          b*                                                                              5.70                                                                              7.51                                                                              9.02                                                                              10.36                                                                             3.35 8.44 12.71                                                                             16.62                                   3-C-3/6-C-3                                                                         L*    29.48                                                                             30.85                                                                             32.07    43.64                                                                              45.80                                                                             48.39                                         a*    3.64                                                                              1.91                                                                              -0.31    5.13 -0.86                                                                             -5.93                                         b*    5.96                                                                              5.78                                                                              5.84     5.86 8.15                                                                              9.89                                    2-C-3/6-C-3                                                                         L*                                                                              32.43                                                                             31.91                                                                             32.48                                                                             32.69                                                                             50.18                                                                              49.73                                                                              49.99                                                                             50.18                                         a*                                                                              1.38                                                                              0.70                                                                              -0.14                                                                             -1.04                                                                             1.18 -1.66                                                                              -4.26                                                                             -8.00                                         b*                                                                              11.72                                                                             9.58                                                                              8.00                                                                              6.91                                                                              20.33                                                                              18.20                                                                              15.83                                                                             13.73                                   2-C-3/5-C-3                                                                         L*    30.85                                                                             29.31                                                                             27.46    48.01                                                                              45.32                                                                             42.10                                         a*    1.57                                                                              1.53                                                                              0.75     0.46 -0.39                                                                             -1.70                                         b*    7.94                                                                              4.00                                                                              -0.94    12.52                                                                              3.44                                                                              -6.29                                   6-C-3/5-C-3                                                                         L*                                                                              34.16                                                                             31.68                                                                             29.83                                                                             27.55                                                                             50.92                                                                              47.95                                                                              44.94                                                                             41.92                                         a*                                                                              -1.68                                                                             -1.00                                                                             -0.74                                                                             0.33                                                                              -10.43                                                                             -8.87                                                                              -7.93                                                                             -5.87                                         b*                                                                              5.28                                                                              3.19                                                                              0.84                                                                              -2.11                                                                             11.45                                                                              5.06 -1.68                                                                             -8.69                                   5-C-3/3-C-3                                                                         L*                                                                              26.41                                                                             26.26                                                                             26.77                                                                             28.01                                                                             38.61                                                                              39.21                                                                              39.60                                                                             40.03                                         a*                                                                              1.04                                                                              2.22                                                                              3.71                                                                              4.58                                                                              -3.54                                                                              0.56 4.44                                                                              8.74                                          b*                                                                              -4.81                                                                             -1.06                                                                             1.27                                                                              3.55                                                                              -15.73                                                                             -11.30                                                                             -6.66                                                                             -2.06                                   __________________________________________________________________________

                                      TABLE 6-2                                   __________________________________________________________________________    RATIO OF                                                                             CH             MCH                                                     MIXTURE                                                                              100/0                                                                             75/25                                                                             50/50                                                                            25/75                                                                             100/0                                                                             75/25                                                                             50/50                                                                             25/75                                       __________________________________________________________________________    A/5-C-3                                                                            L*                                                                              31.01                                                                             29.79                                                                             28.30                                                                            27.42                                                                             45.89                                                                             44.13                                                                             41.98                                                                             40.58                                            a*                                                                              1.55                                                                              1.08                                                                              0.99                                                                             1.16                                                                              -0.36                                                                             -0.79                                                                             -1.54                                                                             -2.03                                            b*                                                                              5.68                                                                              3.21                                                                              0.65                                                                             -1.41                                                                             7.95                                                                              1.75                                                                              -4.31                                                                             -9.58                                       A/2-C-3                                                                            L*    31.10                                                                             32.18                                                                            31.52   46.86                                                                             47.83                                                                             78.70                                            a*    1.53                                                                              1.31                                                                             1.19    0.06                                                                              0.51                                                                              0.79                                             b*    7.12                                                                              9.17                                                                             9.98    11.35                                                                             14.65                                                                             17.68                                       B/3-C-3                                                                            L*                                                                              30.41                                                                             29.88                                                                             29.79                                                                            28.97                                                                             45.19                                                                             44.00                                                                             42.83                                                                             41.46                                            a*                                                                              -0.85                                                                             0.70                                                                              2.18                                                                             3.89                                                                              -7.30                                                                             -2.77                                                                             1.82                                                                              6.67                                             b*                                                                              1.33                                                                              2.47                                                                              3.39                                                                             4.79                                                                              -1.12                                                                             0.13                                                                              0.95                                                                              2.10                                        B/2-C-3                                                                            L*    30.06                                                                             31.85                                                                            31.60   46.23                                                                             47.52                                                                             48.52                                            a*    -0.07                                                                             0.02                                                                             1.09    -4.51                                                                             -2.22                                                                             -0.57                                            b*    3.67                                                                              6.58                                                                             8.75    4.73                                                                              10.23                                                                             15.36                                       C/6-C-3                                                                            L*                                                                              27.62                                                                             29.33                                                                             30.76                                                                            31.60                                                                             39.26                                                                             42.64                                                                             45.19                                                                             47.81                                            a*                                                                              2.73                                                                              1.92                                                                              0.54                                                                             -0.64                                                                             5.19                                                                              0.42                                                                              -3.52                                                b*                                                                              1.51                                                                              2.43                                                                              3.63                                                                             4.23                                                                              -7.02                                                                             -1.60                                                                             2.91                                            C/2-C-3                                                                            L*    28.40                                                                             29.97                                                                            31.27   42.55                                                                             45.19                                                                             47.50                                            a*    2.53                                                                              1.78                                                                             1.84    3.97                                                                              2.86                                                                              2.11                                             b*    4.01                                                                              6.32                                                                             8.76    0.88                                                                              8.05                                                                              14.71                                       __________________________________________________________________________

                                      TABLE 6-3                                   __________________________________________________________________________    RATIO OF                                                                             CH             MCH                                                     MIXTURE                                                                              100/0                                                                             75/25                                                                            50/50                                                                             25/75                                                                             100/0                                                                             75/25                                                                             50/50                                                                             25/75                                       __________________________________________________________________________    D/3-C-3                                                                            L*                                                                              28.78                                                                             28.59                                                                            28.78                                                                             28.40                                                                             44.65                                                                             43.65                                                                             42.72                                                                             41.71                                            a*                                                                              1.28                                                                              2.10                                                                             3.19                                                                              3.68                                                                              0.11                                                                              2.63                                                                              5.69                                                 b*                                                                              4.08                                                                              4.34                                                                             5.06                                                                              5.83                                                                              3.05                                                                              3.13                                                                              3.13                                            D/6-C-3                                                                            L*    30.06                                                                            32.09                                                                             32.50   46.20                                                                             47.99                                                                             49.33                                            a*    0.30                                                                             -0.02                                                                             -0.41   2.49                                                     b*    4.40                                                                             4.74                                                                              4.76    5.21                                                                              7.20                                                                              40.0                                        E/5-C-3                                                                            L*                                                                              30.58                                                                             28.68                                                                            28.11                                                                             26.71                                                                             45.89                                                                             43.76                                                                             42.29                                                                             2.11                                             a*                                                                              3.05                                                                              2.46                                                                             2.21                                                                              1.73                                                                              5.79                                                                              4.21                                                                              2.15                                                 b*                                                                              8.98                                                                              5.70                                                                             2.74                                                                              -0.25                                                                             12.74                                                                             5.55                                                                              -1.00                                           E/6-C-3                                                                            L*    30.32                                                                            31.43                                                                             32.26   46.64                                                                             47.84                                                                             49.01                                            a*    1.70                                                                             0.43                                                                              -0.72   1.67                                                                              -2.22                                                                             -6.93                                            b*    7.72                                                                             6.96                                                                              6.05    13.49                                                                             12.30                                                                             11.89                                       F/5-C-3                                                                            L*                                                                              32.26                                                                             30.50                                                                            29.61                                                                             28.01                                                                             50.00                                                                             47.36                                                                             44.96                                                                             41.75                                            a*                                                                              -0.04                                                                             0.23                                                                             0.37                                                                              0.24                                                                              -3.38                                                                             -3.57                                                                             -3.19                                                                             -3.05                                            b*                                                                              7.64                                                                              5.16                                                                             2.72                                                                              -0.74                                                                             15.67                                                                             7.84                                                                              0.77                                                                              -7.87                                       F/3-C-3                                                                            L*    31.10                                                                            30.23                                                                             30.06   47.85                                                                             45.74                                                                             43.45                                            a*    0.83                                                                             2.44                                                                              3.20    -0.58                                                                             3.05                                                                              7.02                                             b*    7.50                                                                             7.17                                                                              6.87    13.34                                                                             10.17                                                                             7.05                                        __________________________________________________________________________

                                      TABLE 6-4                                   __________________________________________________________________________    RATIO OF                                                                              CH                  MCH                                               MIXTURE 100/0                                                                             75/25                                                                             50/50                                                                             25/75                                                                             0/100                                                                             100/0                                                                             25/75                                                                             50/50                                                                             25/75                                                                              0/100                            __________________________________________________________________________    1-C-3/5-C-3                                                                         L*                                                                              36.95                                                                             34.35                                                                             32.82                                                                             29.54                                                                             26.75                                                                             58.31                                                                             55.10                                                                             50.64                                                                             45.75                                                                              38.63                                  a*                                                                              -2.49                                                                             -1.12                                                                             -0.64                                                                             0.14                                                                              0.57                                                                              -3.17                                                                             -3.15                                                                             -2.98                                                                             -3.17                                                                              -3.58                                  b*                                                                              -0.69                                                                             -1.43                                                                             -2.47                                                                             -3.27                                                                             -5.09                                                                             -2.85                                                                             -4.72                                                                             -7.49                                                                             -10.65                                                                             -16.14                           1-C-3/2-C-3                                                                         L*                                                                              36.95                                                                             35.43                                                                             34.57                                                                             34.12                                                                             32.67                                                                             58.31                                                                             56.65                                                                             54.79                                                                             52.82                                                                              50.85                                  a*                                                                              -2.49                                                                             -0.92                                                                             -0.22                                                                             0.77                                                                              1.03                                                                              -3.17                                                                             -2.03                                                                             -0.93                                                                              0.54                                                                               1.92                                  b*                                                                              -0.69                                                                             1.63                                                                              4.20                                                                              7.78                                                                              12.26                                                                             -2.85                                                                             0.66                                                                              5.23                                                                              11.62                                                                              20.93                            1-C-3/3-C-3                                                                         L*                                                                              36.95                                                                             35.22                                                                             33.14                                                                             30.25                                                                             28.24                                                                             58.31                                                                             55.23                                                                             51.55                                                                             46.89                                                                              40.40                                  a*                                                                              -2.49                                                                             -0.30                                                                             1.27                                                                              3.27                                                                              5.38                                                                              -3.17                                                                             -1.03                                                                             1.73                                                                               5.89                                                                              12.12                                  b*                                                                              -0.69                                                                             0.33                                                                              2.03                                                                              3.82                                                                              6.24                                                                              -2.85                                                                             -1.91                                                                             -0.70                                                                              0.87                                                                               3.23                            1-C-3/5-C-3                                                                         L*                                                                              36.95                                                                             35.29                                                                             35.29                                                                             34.57                                                                             34.05                                                                             58.31                                                                             56.79                                                                             55.11                                                                             53.41                                                                              50.72                                  a*                                                                              -2.49                                                                             -2.41                                                                             -2.11                                                                             -1.45                                                                             -2.36                                                                             -3.17                                                                             -4.33                                                                             -5.79                                                                             -7.53                                                                              -10.50                                 b*                                                                              -0.69                                                                             0.59                                                                              2.06                                                                              3.62                                                                              5.58                                                                              -2.85                                                                             -0.55                                                                             2.31                                                                               6.07                                                                              11.90                            __________________________________________________________________________

[Color Mixing]

Paints were produced by the same method as the preferred embodiment byemploying the pigments of the preferred embodiment sample Nos. 1-C-3(silver), 2-C-3 (gold), 3-C-3 (red), 5-C-3 (blue), 6-C-3 (green). Then,the respective paints were mixed at the pigment ratios shown in Table 5.In the column of `Ratio of Mixture`, A: 3-C-3/6-C-3=50/50, B:6-C-3/5-C-3=50/50, C: 3-C-3/5-C-3=50/50, D: 2-C-3/5-C-3=50/50, E:3-C-3/2-C-3=50/50, and F: 6-C-3/2-C-3=50/50. The mixed paints wereapplied on art papers with a 25 mil-applicator, and then baked anddried. The colors of the obtained paint film were measured by the samemethod as described in the above Colorimetry section. Table 6 shows theresults of the measurement.

In the pigment of the preferred embodiment, various colors can beobtained only by changing the thickness of the titanium dioxide layer,and mixtures of these pigments offer total color variation. Becausevarious colors can be attained only by light interference, the colormixing is made by additive mixture. Thus, clear colors free fromturbidness can be produced. Moreover, as any color can be produced onlyby mica pigment, there is no fear for color separation. In addition,since the pigment of the present invention can be dispersed only bystirring, there is no need to employ the complicated dispersing stepsemployed in the conventional methods, and the man-hour requirement forproducing paints are remarkably reduced.

Obviously, many modifications and variations of the present inventionare possible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described.

What is claimed is:
 1. A method for forming a pigment which producesinterference color, comprising the steps of:plating pearl micacomprising mica with a titanium dioxide layer formed on all surfaces ofsaid mica with a chromium compound, and plating said chrome-plated pearlmica with a metal ar an alloy by electroless plating, whereby a metalliclayer is formed in a scattered manner on an interface between said micaand said titanium dioxide, said metallic layer being formed in gapsbetween particles of said titanium dioxide and around said titaniumdioxide.
 2. A method according to claim 1, wherein said step of platingsaid chrome-plated pearl mica employs silver.
 3. A method according toclaim 2, wherein said silver is plated in an amount in the range of from1 to 100% by weight based of 100% by weight of said pearl mica.
 4. Amethod according to claim 1, wherein the chromium contained in theplated chromium compound is from 0.05-5% by weight based on 100% byweight of said pearl mica.